Horizontal earth boring machine

ABSTRACT

A portable, horizontal earth boring machine which employs two or more hydraulic motors to rotate and advance an auger in an earth boring operation in which the motors are supplied with hydraulic fluid from a single variable displacement pump located remotely from the earth boring machine. The pump is controlled to respond to the loads imposed on the motors to limit the horsepower output of the pump up to a predetermined maximum after which the horsepower is maintained constant until a maximum working load is achieved at the motors. The control is so arranged that demands made by an operator of the earth boring machine in excess of the limits of the pump are negated making possible the selection of an engine to drive the pump of sufficient capacity to meet but not greatly exceed the power requirements of the pump.

United States Patent Martinek Oct. 7, 1975 HORIZONTAL EARTH BORINGMACHINE [75] Inventor: Norman A. Martinek, Milwaukee,

Wis.

[73] Assignee: Koehring Company, Milwaukee,

Wis.

22 Filed: July 5, 1974 [21] Appl. No.: 485,803

[52] US. Cl. 173/152; 60/452; 173/159;

, 175/122 [51] Int. Cl. E21D 9/10 [58] Field of Search 173/152, 159;175/122,

175/62, 171; 299/50, 56; 60/452, 391, 445, 487, 488, DIG. 10

[56] References Cited 3,587,755 6/1971 Slusher 173/159 PrimaryExaminer-Ernest Purser Assistant ExaminerWilliam F. Pate, Ill

Attorney, Agent, or FirmAndrew .1. Beck 57] ABSTRACT A portable,horizontal earth boring machine which employs two or more hydraulicmotors to rotate and advance an auger in an earth boring operation inwhich the motors are supplied with hydraulic fluid from a singlevariable displacement pump located remotely from the earth boringmachine. The pump is controlled to respond to the loads imposed on themotors to limit the horsepower'output of the pump up to a predeterminedmaximum after which the horsepower is maintained constant until amaximum working load is achieved at the motors. The control is soarranged that demands made by an operator of the earth boring machine inexcess of the limits of the pump are negated making possible theselection of an engine to drive the pump of sufficient capacity to meetbut not greatly exceed the power requirements of the pump.

15 Claims, 6 Drawing Figures US. Patent Oct. 7,1975 Sheet 1 on 3,910,358

US. Patent Oct. 7,1975 SheetZ 0f3 3,910,358

HORIZONTAL EARTH BORING MACHINE BACKGROUND OF THE INVENTION Thisinvention relates to portable, horizontal earth boring machines and,more particularly, to a hydraulically operated earth boring machine inwhich the power source for the machine may be disposed remotely inselected positions.

Horizontal earth boring machines are normally mounted in workingposition on tracks or rails which are positioned in an open ditch sothat the machine is advanced as a rotating auger drills a horizontalbore in the earth. To properly control both the advance of the auger andthe rotation of the auger, the operator of the machine must be in closeproximity to the auger where he can view the operation. Consequently, heis usually positioned in a ditch together with the earth boring machine.

Since horizontal earth boring machines are usually of the portable type,they employ internal combustion engines as the power source. Thepositioning of such engines in the confines of a ditch results not onlyin a high noise level, but also can be a health hazard to an operatorworking adjacent to the engine. To avoid these problems and also tocomply with certain government regulations, complex exhaust and enginemuffler arrangements have been employed which add to the complexity andsize of the earth boring apparatus and make it difficult to properlylocate it in a working position.

Another solution to the problem has been to use a pair of hydraulicpumps, one for driving a hydraulic motor which rotates the earth boringauger and the other to supply hydraulic fluid for reciprocatinghydraulic actuators which acts to advance or retract the auger as it isrotated in the earth. Both of the pumps are driven by internalcombustion engines which can be positioned remotely from the earthboring auger and, as a consequence, can be positioned at ground levelabove the ditch in which the operator is located.

The operator of the machine remains located in the ditch to regulate thespeed and direction of rotation as well as the advance and retraction ofthe auger. Such operation can subject the pumps to unduly largehydraulic loads which can cause the driving engine to stall. This, ofcourse, requires the operator to leave his work station in the ditch andto restart the engine after which he must return to his work position inproximity to the controls of the machine. Alternatively, the internalcombustion engine for driving the pumps can be selected of a size largeenough to accommodate the maximum loads. This, of course, requires anexcessively large internal combustion engine and adds to the expense ofthe equipment.

SUMMARY OF THE INVENTION This invention contemplates the use of a singlehydraulic pump to furnish pressure fluid to hydraulic motor means torotate an earth boring auger and to reciprocate the auger using controlswhich are so arranged that demands in excess of the capacity of the pumpto rotate or to advance the auger, or both, are rejected and thecapacity of the pump, and therefore the capacity of the internalcombustion engine driving the pump, cannot be exceeded. The singlehydraulic pump utilizes controls responsive to the higher of the loadpressures required to either rotate the auger or to advance the augerwhich places a limit on the displacement of the pump and, consequently,on its output.

A horizontal earth boring machine has been provided in which the powersource may be located remotely from the driven earth boring elements.using the power source. The functions of rotating the auger and ofadvancing the auger can be conducted independently, simultaneously andefficiently under the control of an operator located in close proximityto the auger where he may observe and control its operation. Thehydraulic pump for supplying the hydraulic fluid for the rotatinghydraulic motor and for the hydraulic actuators advancing the auger is asingle, variable displacement hydraulic pump of the pressure compensatedtype which responds to the higher of the working pressures existing inthe auger rotating motor or in the auger advancing hydraulic actuatorsto limit the power output up to a predetermined level of pump capacitywhich determines the size and power capacity of the internal combustionengine required to power the hydraulic pump.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view showingan earth boring machine embodying the present invention, located in aworking position with the power source located remotely from the workingposition;

FIG. 2 is a side elevation of the horizontal earth boring machine;

FIG. 3 is a top view of the machine shown in FIG. 2;

FIG. 4 is a sectional view taken on line 4-4 in FIG. 3;

FIG. 5 is a schematic diagram of the hydraulic circuit used to controlthe earth boring machine; and

FIG. 6 is a curve depicting the characteristics of the pump employed tosupply power to the earth boring machine.

DETAILED DESCRIPTION Referring to the drawings, and particularly to FIG.1, a preferred embodiment of the invention includes a horizontal earthboring machine 10 which is operated to rotate an auger 12 and to advancethe auger while it is being rotated to form a bore in the earth. Themachine can also be used to advance a casing member 14 which forms alining to the bore formed by the auger l2 and serves to convey thematerial cut by the auger rearwardly from the bore which is beingformed.

The horizontal earth boring machine includes a base structure 16 whichis made up of a basic track section 18 and one or more extension tracksections 20 and 22. The basic track section 18 includes a pair ofgenerally channel-shaped rail members 24 and 26 which are held apart inparallel spaced relationship to each other by a plurality of crossbraces 28 which may be rigidly attached to the rails 24 and 26 as bywelding or the like. The cross braces 28 also act to engage the groundand to support the rails generally horizontally and parallel to the axisof rotation of the auger l2 and to the bore which is to be formed in theearth. The cross members 28 at opposite ends of the base structure 18are provided with lift rings 30 to which lifting equipment may beconnected to raise and lower the base track structure relative to theditch.

The rear or left end of the basic track structure 18, as viewed in FIGS.2 and 3, is provided with a cross member 32 hich acts as a backstop andthe other, or right end of the basic track structure 18, is providedwith connecting plates 34 associated with the tracks 24 and 26 forsecuring the basic track structure 18 to an extension track structure20. The extension track structure 20 also includes a pair of tracks 24and 26, cross members 28 and lift rings 30 by which the extensionsection 20 may be raised and lowered relative to the ditch in which themachine is to operate. Similarly connecting plates 34 may be located atthe joint between the extension track sections 20 and 22 to secure themrelative to each other.

A carriage structure indicated generally at 36 is disposed on top of thetracks 24 and 26 for longitudinal sliding movement relative to thelatter. The carriage structure 36 includes a pair of anchor plates 38associated with the track 24 and a similar pair of anchor plates 40associated with the track 26 which serve to secure the carriage 36against vertical movement relative to the tracks 24 and 26.

The carriage 36 supports a reversible hydraulic motor 42 which serves todrive a gear reduction unit 44 which in turn rotates the auger 12.

The carriage structure 36 is moved longitudinally of the tracks 24 and26 by means of a pair of hydraulic actuators 48, each of which has acylinder portion pivotally connected to the carriage 36 and a rodportion 52 pivotally connected to an anchor structure 54. The anchorstructure 54 extends transversely to the tracks 24 and 26. One end ofthe anchor structure 54 is provided with a pair of pins 56 which areadapted to be inserted and retracted from selected, adjacent pairs ofholes 58 in the track 24. Similarly, the other end of the anchorstructure 54 is provided with pins 56 adapted to be inserted intoselected ones of pairs of openings 58 in the track 26. Pins 56 arerigidly connected to a pin bracket 63 and are adapted to be movedvertically into and out of the openings 58 by means of a lever 64 whichserves to raise and lower the pin bracket 63 and the pins 56 throughmeans of links 66.

The hydraulic actuators 48 are of the double-acting type, and thetransmission of hydraulic fluid to one end of the actuators 48 causesextension of the rods 52 so that the carriage structure is moved to theright relative to the anchor structure 54 as viewed in FIGS. 2 and 3.Similarly, the transmission of hydraulic fluid to the left end of thehydraulic actuators 48 serves to retract the rods 52 so that thecarriage structure 36 moves to the left. Such extension and retractionof the piston rods 52 serves to move the carriage structure 36 relativeb the anchor structure 54 to either advance or retract the auger 12.

The carriage structure 36 is also provided with a casing pusher whichserves to engage one end of the casing 14 and to hold it nonrotatablyrelative to the auger 12. Upon advancement of the carriage 36 to theright, as viewed in FIGS. 2 and 3, the casing pusher 70 serves toadvance the casing 14 together with the auger 12 so that, as a bore isformed in the earth, the casing 14 lines the bore. The casing 14 alsoacts to convey the material cut by the auger 12 from the open end of thecasing 14 toward the casing pusher from which it is discharged by meansof rotating paddles 71.

A pair of generally vertical bar structures 76 are disposed at oppositesides of the carriage 36. The bar members 76 serve as a lift cage bywhich the carriage member may be lowered into a ditch or raised from aditch by lifting machinery such as a crane.

Disposed on the bar member 76 are control levers 78 and 80 operatingvalve controls to be described. The carriage member 36 also includes anoperators platform 82 at which an operator may position himself foroperation of the valve control levers. The platform is positionedrearwardly of the direction of auger advance for good visibility ofauger operation.

The hydraulic motor 42 and the hydraulic actuators 48 receive hydraulicfluid which is controlled manually by the operator located on theplatform by manipulation of a pair of valve operating levers 78 and 80.The Iever 78 is used to control a directional valve mechanism regulatingthe direction of rotation and speed of the motor 42 and the lever 80 isused to similarly control the operation of the hydraulic actuators 48 toadvance or retract carriage 36.

Referring now to FIG. 1, the source of hydraulic fluid pressure foroperation of the hydraulic motor 42 and of the hydraulic actuators 48 isincorporated in a power assembly designated generally at 86. The powerassembly 86 includes a base frame structure 88 in which an internalcombustion engine 90 is mounted to drive a hydraulic pump 92 which isindicated in FIG. 5. The base structure 88 also serves to support abattery 96, a fuel tank 98 and a reservoir 100 for the hydraulic fluid.A lift bar 101 is rigidly secured to the base structure 88 so that allof the components mounted thereon may be lifted and positioned by meansof a crane or the like at some point adjacent to the machine 10 butpreferably at ground level and out of the ditch in which the machine 10is being operated.

The hydraulic pump 92 is connected to a control valve 102 manuallyactuated by lever 78 and a control valve 104 manually actuated by thelever 80 by means of a delivery line 106. A line 108 serves as a returnline, and a line 110 serves as a control signal line.

Hydraulic Circuit Referring now to FIG. 5 schematically illustrating theclosed-center hydraulic system employed in operating the horizontalearth boring machine 10, the variable displacement pump 92 driven by theinternal combustion engine 90 receives hydraulic fluid from thereservoiry100 through a line 112 for delivery by the pump 92 through theline 106 to branch supply lines 116 and 118. The supply line 116delivers hydraulic fluid to a control circuit which is utilized tocontrol the doubleacting hydraulic actuators 48 by manual movement ofthe control lever 80. The supply line 118 delivers hydraulic fluid to acontrol circuit for controlling the direction and speed of the hydraulicmotor 42 which rotates the auger 12.

Referring to the control circuit for controlling the hydraulic actuators48, movement of the control lever 80 controls the directional four-waycontrol valve 104. Movement of the control lever 80 to the left, asviewed in FIG. 5, is effective to supply hydraulic fluid from the line116 to a pressure compensating valve 122 and through a line 124 to thedirectional valve 104. The valve 104 controls the flow of fluid to aline 126 to the head end of both of the actuators 48, forming part ofthe hydraulic actuators 48. Delivery of hydraulic fluid under pressurein this manner causes the hydraulic actuator rods 52 to move to theleft, as seen in FIG. 5 and also in FIG. 2, to advance the carriage 36to the right in an earth boring direction.

As the rods 52 of the hydraulic actuators 48 move to the left. hydraulicfluid is ejected from the rod ends of the cylinders 50 through line 130to the control valve 104 from which it passes to the return line 108 andback to the reservoir 100.

Movement of the control lever 80 to the right to move valve 104 from itsneutral position shown in FIG. 5 causes hydraulic fluid to be deliveredto the valve 104 and through the line 130 to the rod end of thecylinders 50, causing the piston rods 52 to move to the left relative tothe cylinders 50. At the same time fluid is ejected through the lines126 to the control valve 104 and to the return line 108 back to thereservoir 100.

When the control valve 104 is operated by moving the lever 80 to eitherthe left or the right of the neutral position in which the valve isshown in the drawing, the working pressure in either of the lines 126 or130 which is being delivered to the hydraulic actuators 48 also is madeavailable in a pilot signal line 134. The pilot control pressure in theline 134 is made available to control the pressure compensating valve122 through a line 136 and also is made available to a pressure reliefvalve 138 by way of hydraulic line 140. The pressure relief valve 138 isconnected to the return line 108 by way of a line 142. The pressurerelief valve 138 serves to relieve the pressure in the working end ofthe hydraulic actuators 48 when the pressure exceeds some predeterminedmaximum which, for example, can be to the order of 2,300 psi.

The hydraulic fluid pressure in the pilot signal line 134 from thehydraulic actuator control valve 104 communicates through a one-waycheck valve 144 to a line 146 which communicates with a signal port 148associated with the pump 92 and its controls.

Referring now to the control valve circuit associated with the hydraulicmotor 42, hydraulic fluid is delivered through the line 118 through apresssure compensating valve 150 which is similar to the pressurecompensating valve 122. Hydraulic fluid from the pressure compensatingvalve 150 is delivered to a control valve 102 through a line 154 and isreturned through a line 156 to the return line 108 and to the reservoir100. The valve 102 is identical to the directional four-way valve 104and movement of the control lever 78 to the right causes delivery ofhydraulic fluid from the line 154 to a line 158 to cause rotation of themotor 42 in one direction. At the same time hydraulic fluid is exhaustedfrom the motor 42 through a return line 160, through the valve 152 andto the line 156 communicating with the return line 132 and the reservoir100. The movement of the control lever 78 to the left causes delivery ofthe hydraulic fluid from the line 154 through the valve 102 and to theline 160 causing the motor 42 to rotate in the opposite direction. Fluidfrom the motor 42 is returned by way of the lines 158, 156 and 108 tothe reservoir 100.

As in the case of the control valve 104, the working pressure deliveredthrough the valve 102 to the motor 42 is made available in a pilotsignal line 162 whenever the control valve 102 is moved to the left orto the right of its neutral or center position. Pilot signal pressurefrom the line 162 is made available to control the pressure compensatingvalve 150 through a line 164. The pilot signal pressure in the line 162,which is at the working pressure of the motor 42, communicates through acheck valve 166 to a line 168 and the signal line 146 to the signal port148.

A pressure relief valve 170 is disposed between the supply line 118 andthe return line 108 to limit the maximum pressure which can be madeavailable to the motor 42, for example, 3000 psi.

The check valve 144 associated with the control circuit for thehydraulic actuators 48 and the check valve 166 associated with thecontrol circuit for the hydraulic motor 42 are so arranged that thehigher of the working pressures existing in either the motor 42 or inthe'actuators 48 is made available at the signal port 148.

Pump Control Circuit The pump 92 is a pressure compensated variabledisplacement pump 92 of the axial piston type which includes aswashplate indicated at 174 the angle of which is under the control of apump servo piston 176. Increase of piston stroke in response to increaseof signal pressures results in an increase in the swashplate angle and acorresponding increase ,in displacement of the pump 92. The pump servopiston 176 is under the control of a pressure compensating circuitdesignated generally at 178 which responds to a differential in pressureat the signal port 148 and in an output pressure signal line 180communicating with the output line 106 from the pump 92. The circuit 178operates to maintain the pressure differential at signal port 148 andsignal line 180 at some predetermined constant level which could beselected, for example, to be 200 psi. If the working pressure downstreamof the valves 102 and 104 and at the signal port 148 changes, theposition of the pump servo piston 176 changes to regulate thedisplacement of the pump 92 to maintain a constant pressure differentialat the signal port 148 and the high pressure signal line 180.

The operator of the earth boring machine 10 can sense only the velocityof flow due to his control of the valves 102 and 104 but cannot sensethe magnitude of the pressure demanded by the load. To prevent ahorsepower overload from occurring, the control circuit 178 is providedwith a horsepower limiting control indicated at 184 which functionsautomatically to reject any requirement which is made manifest byoperation of the valves 102 and 104 to require more power than isavailable in the system. The horsepower limiting device 184 is biased bya spring 186 which is grounded against an arm 188 connected to theswashplate 174. As the pump 92 increases displacement due to an increasein angle of the swashplate the power limiter spring is relaxed requiringless load pressure in the line 180 to overcome the force generated bythe spring 186, and the load pressure at which the horsepower limitingdevice shifts is inversely proportional to the displacement of the pump92.

The control circuit also includes a valve 192 which is connected to thesystem so that the pump control differential pressure at the signal port148 and in the high pressure signal line 180 act across the spool urgingit to the right as seen in FIG. 5. Since the control differential ismaintained at a constant level during operation, the force on the spooldue to the pressure differential remains constant throughout the rangeof operation. A biasing spring 194 is employed to keep the spool in itsnormal position. When the directional control valves 102 and 104 are intheir neutral position, the output of the pump 92 is blocked andpressure in the high pressure signal line 180 will rise. This pressureacts on the valve 192 and the rate of the spring 194 can be selected torequire an increase in pressure above the normal control differentialpressure at the signal part 148 and the high pressure line 180 toovercome the spring load. Once the delivery line pressure meets thispressure requirement, the valve 192 shifts to the left to communicate afixed bypass orifice 196 with a line 198 to the reservoir 100. Theorifice 196 is selected to be only small enough to maintain enoughpressure drop across the orifice to keep the valve 192 shifted. Sincethe valve pressure drop is also the pump control differential, the pump92 is commanded to a minimum stroke at a low working pressure. By way ofexample, the pump could be controlled to deliver one or two gallons offluid per minute at a pressure of 400 to 500 psi.

Operation of the control circuit 178, shown in FIG. 5, can best beunderstood by reference to FIG. 6 which illustrates the operatingcharacteristics of the pump 92 in terms of hydraulic fluid flowdesignated by the coordinate Q and the pressure which is designated bythe coordinate P. The variable displacement pump is designed andcontrolled to deliver up to a maximum of 21 gallons per minute and up toa pressure of 2000 psi which is designated by that portion of thecharacteristic curve between points A and B. Maximum flow to either ofthe actuators 48 or to the motor 42 is a function of the fluid capacityof the pump 92 and the maximum metering characteristics of valves 102and 104 determined by the stroke of the valves from their neutralposition.

Beyond the points B to the point C the maximum horsepower output of thepump, which is a product of flow and pressure, is maintained constant bymeans of the horsepower limiting valve 184 which modifies thedisplacement of the pump 92 as the working pressure at the signal port148 increases. The maximum pressure of the system occurs at point C atwhich point the pressure relief valve 170 in the motor circuit opens. Byway of example, the pressure at this point could be 3000 psi with fluidflow to the order of 10 or I 1 gallons per minute.

The point E on the curve denotes the condition in which both of thedirectional control valves 102 and 104 are in their neutral position andthe pump 92 is restricted to limit flow at a relatively moderatepressure, for example, one to two gallons per minute at 400 to 500 psi.

The maximum torque required to drive the pump 92 is determined by theload occurring at point B at which the maximum flow of the system occursat its highest pressure. The engine 90 to drive the pump 92 is selectedto accommodate this load so that when it occurs the engine will notoverload and stall.

Operation The horizontal earth boring operation is begun by placing themachine 10 in a ditch adjacent to the location where the bore is to beformed in the earth and by placing the power assembly 86, preferably toone side of the ditch, in a remote location. The machine 10 and thepower assembly 86 are then connected by means of the delivery line 106the return line 108 and the signal line 110.

With the pump 92 being driven by the internal combustion engine 90 andwith the control valves 102 and 104 in their neutral position, a smallquantity of hydraulic fluid is being circulated at a relatively lowpressure in the lines between the pump 92 and the control valves 102 and104. Movement of the control lever 78 associated with the control valve102 is effective to deliver hydraulic fluid to the variable hydraulicmotor 42 to initiate rotation of the auger 12. Depending on the positionof the valve 104 and the resistance to rotation of the auger in theearth, the speed of rotation is controlled. The working load will bemade apparent at the control system by an increase in pressure in thesignal line 146 and at the signal line port 148. The differential inpressure at the port 148 and in the output line 106 will adjust the pump92 to deliver hydraulic fluid to the line 106 at a pressureapproximately 200 psi higher than the pressure in the signal line 146which represents the working pressure downstream of the valve 102. Withthe auger l2 rotating, the control lever 80 may be moved to the right,as seen in FIG. 5, to cause advance of the carriage 36 together with theauger 12. If the carriage 36 is advanced at a speed requiring more thanthe remaining fluid of the system and at a pressure or load whichdevelops a working pressure less than the working pressure of the motor42, the flow of fluid to the motor 42 will be restricted and,consequently, the augers rotation will be retarded. Slowing of rotationof the auger 12 will be apparent to the operator, and, if desired, hemay retard the demanded speed of operation of the motor 40 or of theactuators 48 to make fluid flow available in the other of thesecircuits.

If the valves 102 and 104 are simultaneously stroked to utilize the fullflow of the pump and to create a working pressure at one of thefunctions, for example the motor 42, in excess of 2000 psi, thehorsepower control functions to maintain the maximum output orhorsepower, which is the product of flow and pressure, at a relativelyconstant value as depicted in the curve of FIG. 6 between points B andC. As the working pressure increases, the flow decreases. At the pointC, for example, the horsepower output of the pump can be equal to orslightly less than the output at point B and the engine driving thevariable displacement pump 92 will not be overloaded or stall.

It will be noted that each of the valves 102 and 104 may be operatedindependently of each other and the valve 102 is protected by a pressurerelief valve and the control valve 104 of the actuator circuit isprotected by a pressure relief valve 138.

Although two valves 102 and 104 have been disclosed to control twodifferent functions of the earth boring machine 10, it should beapparent that additional functions and control circuits can be added andoperated independently of the other control circuits.

A horizontal earth boring machine has been provided in which the earthboring functions, such as rotation of an auger and advancing of theauger into a bore which is to be formed, may be conducted at onelocation, for example in a ditch, and the power source for conductingsuch functions may be located remotely and to one side and out of theditch. The functions, such as rotating the auger and advancing the augeror bore casing, can be conducted independently or simultaneously underthe control of an operator located close to the boring operation andremote from the power source. The hydraulic pump for supplying thehydraulic fluid for conducting the required operations is provided by asingle variable displacement hydraulic pump in which the maximumhorsepower is limited by a pump control circuit which permits theoperator to operate the earth boring machine without concern forexceeding the capacity of the pump since the control circuit will negateany demands which are made by the operator that exceed the capacity ofthe system. This makes possible the selection of a power source to drivethe hydraulic pump for the earth boring machine of sufficient but notexcessive capacity to supply the necessary pump output and at thesametime so that it will not be overloaded and stall.

I claim:

1. A generally horizontal earth boring machine apparatus comprising: agenerally horizontally disposed earth boring auger, a hydraulic motoroperatively connected to said auger to rotate the latter in oppositedirections, hydraulic actuator means operatively connected to said augerto move the latter axially in opposite directions, a variabledisplacement pump located in a selected position independently of theposition of said motor and actuator means and having a discharge fordelivering hydraulic fluid to said motor and actuator means, firstdirectional control valve means controlling communication between saidpump discharge and said motor, second directional control valve meanscontrolling communication between said pump discharge and said actuatormeans, hydraulic means responsive to hydraulic pressure to vary thedisplacement of said pump, control means for delivering hydraulic fluidto said hydraulic means, said control means having a pair of signalports, one of said signal ports being in communication with said pumpdischarge, first regulating means between said motor and the other ofsaid signal ports and being responsive to pressure in said motor greaterthan in said actuator to communicate pressure to said other of saidsignal ports, second regulating means operatively disposed between saidactuator means and said other of said signal ports and being responsiveto pressure in said actuator means greater than in said motor tocommunicate pressure to said other of said signal ports, said hydraulicmeans being operative to vary the displacement of said pump to maintaina predetermined pressure differential between said pair of signal portsup to a predetermined pressure level at said pump discharge.

2. The combination of claim 1 and further comprising power limitingmeans communicating with said signal ports and being operative beyondsaid predetermined pressure level at said output port to deliverhydraulic fluid to said hydraulic means to decrease the displacement ofsaid pump as pressure at said output port increases above saidpredetermined level.

3. The combination of claim 1 and further comprising power means fordriving said variable displacement pump and in which said power meansand said variable displacement pump are disposed in selected positionsremotely from said earth boring auger.

4. The combination of claim 1 in which said control means includes powerlimiting means operative beyond said predetermined pressure level tomaintain the product of hydraulic fluid flow and hydraulic pressure at asubstantially constant value.

5. The combination of claim 1 in which said first and second directionalcontrol valve means each include an inlet for receiving fluid from saidpump and an outlet for returning fluid to said pump, and furthercomprising pressure relief valve means between the inlet and the outletof said first directional control valve means to determine the maximumpressure at said outlet port.

6. The combination of claim 5 further comprising pressure relief valvemeans between the inlet and the outlet of said second directionalcontrol valve means operable to open at a preaaure greater than saidmaximum pressure at said outlet port.

7. The combination of claim 1 in which said first and second directionalcontrol valve means are operable simultaneously and independently ofeach other.

8. A horizontal earth boring machine comprising:

a carriage supported for horizontal movement, an elongated earth boringauger supported relative to said carriage for rotation relative thereto,a hydraulic motor operatively connected to said auger to rotate thelatter in opposite directions, hydraulic actuator means operativelyconnected to said carriage to move the latter in opposite directions toadvance and retract said auger, a pump having a discharge for deliveringhydraulic fluid to said motor and said actuator means, first directionalcontrol valve means between said pump discharge and said motor forcontrolling the direction of rotation of said auger, second directionalcontrol valve means between said pump discharge and said actuator meansfor controlling the direction of movement of said carriage, adjustingmeans movable to vary the displacement of said pump, hydraulic servopiston means connected to said adjusting means and being responsive tohydraulic pressure to move the latter, control means for deliveringhydraulic fluid to said servo piston means, said control means having apair of signal ports, one of said signal ports being in communicationwith said pump discharge, first regulating means between said motor andthe other of said signal ports and being responsive to pressure in saidmotor greater than said actuator to communicate pressure to said otherof said signal ports, second regulating means operatively disposedbetween said actuator means and said other of said signal ports andbeing responsive to pressure in said actuator means greater than in saidmotor to communicate pressure to the other of said signal ports, saidcontrol means being operative to deliver hydraulic fluid to said servopiston means to vary the displacement of said pump to maintain apredetermined pressure differential between said pair of signal ports upto a predetermined pressure level at said pump discharge.

9. The combination of claim 8 and further comprising power limitingmeans communicating with said signal ports and being operative beyondsaid predetermined pressure level at said pump discharge to deliverhydraulic fluid to said piston means to decrease the displacement ofsaid pump as pressure at said output port increases beyond saidpredetermined level.

10. The combination of claim 9 in which an adjusting means is moved todecrease displacement of said pump as said pressure increases tomaintain the product of displacement and pressure at a substantiallyconstant value.

11. The combination of claim 9 in which said power limiting means isoperatively connected to said adjusting means to decrease thedisplacement of said pump in response to an increase in pressure at saidpump discharge and said other of said signal ports.

12. A generally horizontal earth boring machine comprising: a generallyhorizontal earth boring auger, a hydraulic motor operatively connectedto said auger to rotate the latter in opposite directions, hydraulicactuator means operatively connected to said auger to move the latteraxially in opposite directions, a variable displacement pump dischargefor delivering hydraulic fluid to said motor and actuator means, firstand second directional control valve means operatively disposed betweensaid pump discharge and said motor and between said pump discharge andactuator means, respectively, and each being movable from a neutralposition to control the delivery of fluid to said motor and to saidactuator means in proportion to the amount of movement of said valvemeans from said neutral position, hydraulic means responsive tohydraulic pressure to vary the displacement of said pump discharge,control means for delivering hydraulic fluid to said hydraulic means,said control means having a pair of signal ports, one of said signalports being in communication with said pump discharge, means for deliverthe highest of the fluid pressures downstream of said first and secondcontrol valve means to the other of said signal ports, said hydraulicmeans being operative to vary the displacement of said pump to maintaina predetermined pressure differential between said pair of signal portsup to a predetermined pressure level of said pump discharge, and powerlimiting means communicating with said signal ports and being operativebeyond said predetermined pressure level at said pump discharge todeliver hydraulic fluid to said hydraulic means to decrease displacementof said pump as the pressure increases above said predetermined pressurelevel.

13. The combination of claim 12 in which said power limiting means isoperative to maintain the flow of hydraulic fluid and the pressurethereof at said output port at a substantially constant value.

14. The combination of claim 12 in which said first and second controlvalve means are operative in said neutral positions of both of saidcontrol valve means to increase the pressure differential between saidpair of signal ports to a predetermined amount above said predeterminedpressure differential, and regulating means responsive to said lastmentioned increase to actuate said hydraulic means to a positiondecreasing displacement of said pump to a minimum.

15. The combination of claim 12 in which said control valve means areoperative in their neutral position to increase pressure at said one ofsaid signal ports to increase pressure differential between said pair ofsignal ports to a value above said predetermined pressure differential,and regulating means operatively connected to said hydraulic means toactuate the latter to a position decreasing displacement of said pump toa minimum in response to an increase in pressure differential to saidlevel above said predetermined pressure differential.

1. A generally horizontal earth boring machine apparatus comprising: agenerally horizontally disposed earth boring auger, a hydraulic motoroperatively connected to said auger to rotate the latter in oppositedirections, hydraulic actuator means operatively connected to said augerto move the latter axially in opposite directions, a variabledisplacement pump located in a selected position independently of theposition of said motor and actuator means and having a discharge fordelivering hydraulic fluid to said motor and actuator means, firstdirectional control valve means controlling communication between saidpump discharge and said motor, second directional control valve meanscontrolling communication between said pump discharge and said actuatormeans, hydraulic means responsive to hydraulic pressure to vary thedisplacement of said pump, control means for delivering hydraulic fluidto said hydraulic means, said control means having a pair of signalports, one of said signal ports being in communication with said pumpdischarge, first regulating means between said motor and the other ofsaid signal ports and being responsive to pressure in said motor greaterthan in said actuator to communicate pressure to said other of saidsignal ports, second regulating means operatively disposed between saidactuator means and said other of said signal ports and being responsiveto pressure in said actuator means greater than in said motor tocommunicate pressure to said other of said signal ports, said hydraulicmeans being operative to vary the displacement of said pump to maintaina predetermined pressure differential between said pair of signal portsup to a predetermined pressure level at said pump discharge.
 2. Thecombination of claim 1 and further comprising power limiting meanscommunicating with said signal ports and being operative beyond saidpredetermined pressure level at said output port to deliver hydraulicfluid to said hydraulic means to decrease the displacement of said pumpas pressure at said output port increases above said predeterminedlevel.
 3. The combination of claim 1 and further comprising power meansfor driving said variable displacement pump and in which said powermeans and said variable displacement pump are disposed in selectedpositions remotely from said earth boring auger.
 4. The combination ofclaim 1 in which said control means includes power limiting meansoperative beyond said predetermined pressure level to maintain theproduct of hydraulic fluid flow and hydraulic pressure at asubstantially constant value.
 5. The combination of claim 1 in whichsaid first and second directional control vAlve means each include aninlet for receiving fluid from said pump and an outlet for returningfluid to said pump, and further comprising pressure relief valve meansbetween the inlet and the outlet of said first directional control valvemeans to determine the maximum pressure at said outlet port.
 6. Thecombination of claim 5 further comprising pressure relief valve meansbetween the inlet and the outlet of said second directional controlvalve means operable to open at a preaaure greater than said maximumpressure at said outlet port.
 7. The combination of claim 1 in whichsaid first and second directional control valve means are operablesimultaneously and independently of each other.
 8. A horizontal earthboring machine comprising: a carriage supported for horizontal movement,an elongated earth boring auger supported relative to said carriage forrotation relative thereto, a hydraulic motor operatively connected tosaid auger to rotate the latter in opposite directions, hydraulicactuator means operatively connected to said carriage to move the latterin opposite directions to advance and retract said auger, a pump havinga discharge for delivering hydraulic fluid to said motor and saidactuator means, first directional control valve means between said pumpdischarge and said motor for controlling the direction of rotation ofsaid auger, second directional control valve means between said pumpdischarge and said actuator means for controlling the direction ofmovement of said carriage, adjusting means movable to vary thedisplacement of said pump, hydraulic servo piston means connected tosaid adjusting means and being responsive to hydraulic pressure to movethe latter, control means for delivering hydraulic fluid to said servopiston means, said control means having a pair of signal ports, one ofsaid signal ports being in communication with said pump discharge, firstregulating means between said motor and the other of said signal portsand being responsive to pressure in said motor greater than saidactuator to communicate pressure to said other of said signal ports,second regulating means operatively disposed between said actuator meansand said other of said signal ports and being responsive to pressure insaid actuator means greater than in said motor to communicate pressureto the other of said signal ports, said control means being operative todeliver hydraulic fluid to said servo piston means to vary thedisplacement of said pump to maintain a predetermined pressuredifferential between said pair of signal ports up to a predeterminedpressure level at said pump discharge.
 9. The combination of claim 8 andfurther comprising power limiting means communicating with said signalports and being operative beyond said predetermined pressure level atsaid pump discharge to deliver hydraulic fluid to said piston means todecrease the displacement of said pump as pressure at said output portincreases beyond said predetermined level.
 10. The combination of claim9 in which an adjusting means is moved to decrease displacement of saidpump as said pressure increases to maintain the product of displacementand pressure at a substantially constant value.
 11. The combination ofclaim 9 in which said power limiting means is operatively connected tosaid adjusting means to decrease the displacement of said pump inresponse to an increase in pressure at said pump discharge and saidother of said signal ports.
 12. A generally horizontal earth boringmachine comprising: a generally horizontal earth boring auger, ahydraulic motor operatively connected to said auger to rotate the latterin opposite directions, hydraulic actuator means operatively connectedto said auger to move the latter axially in opposite directions, avariable displacement pump discharge for delivering hydraulic fluid tosaid motor and actuator means, first and second directional controlvalve means operatively disposed between said pump discharge and saidmotor and between said Pump discharge and actuator means, respectively,and each being movable from a neutral position to control the deliveryof fluid to said motor and to said actuator means in proportion to theamount of movement of said valve means from said neutral position,hydraulic means responsive to hydraulic pressure to vary thedisplacement of said pump discharge, control means for deliveringhydraulic fluid to said hydraulic means, said control means having apair of signal ports, one of said signal ports being in communicationwith said pump discharge, means for deliver the highest of the fluidpressures downstream of said first and second control valve means to theother of said signal ports, said hydraulic means being operative to varythe displacement of said pump to maintain a predetermined pressuredifferential between said pair of signal ports up to a predeterminedpressure level of said pump discharge, and power limiting meanscommunicating with said signal ports and being operative beyond saidpredetermined pressure level at said pump discharge to deliver hydraulicfluid to said hydraulic means to decrease displacement of said pump asthe pressure increases above said predetermined pressure level.
 13. Thecombination of claim 12 in which said power limiting means is operativeto maintain the flow of hydraulic fluid and the pressure thereof at saidoutput port at a substantially constant value.
 14. The combination ofclaim 12 in which said first and second control valve means areoperative in said neutral positions of both of said control valve meansto increase the pressure differential between said pair of signal portsto a predetermined amount above said predetermined pressuredifferential, and regulating means responsive to said last mentionedincrease to actuate said hydraulic means to a position decreasingdisplacement of said pump to a minimum.
 15. The combination of claim 12in which said control valve means are operative in their neutralposition to increase pressure at said one of said signal ports toincrease pressure differential between said pair of signal ports to avalue above said predetermined pressure differential, and regulatingmeans operatively connected to said hydraulic means to actuate thelatter to a position decreasing displacement of said pump to a minimumin response to an increase in pressure differential to said level abovesaid predetermined pressure differential.